1. Field of the Invention
This invention is related to the construction of liquefied natural gas vessels and more particularly to a unique scaffolding construction and arrangement for finishing the inside of an LNG vessel.
2. Description of the Prior Art
Prior art scaffolding arrangements for the inside of LNG vessels have been specially constructed for each job. They have utilized cross bracing which limits work area mobility and have not provided for adjustable outrigger sections.
The interior of LNG vessels must be finished with a relatively thick coating of thermal insulation which has a built up thickness of around 14 inches. This insulation must be securely attached to the inner walls of the vessel. The insulation comes in relatively large panels. The insulation panels are made of fiber glass, wooden grounds and wooden panels. Some standard sizes of panels are 10' .times. 6' .times. 7", 6' .times. 6' .times. 7", and 6' .times. 4' .times. 7". Angled panels that fit in the corners and ends of the tanks are also supplied. The edges of the panels can be angled so that the installed panels fit the contour of the vessel. Depending on the panel design the size of panel can vary, however, in most instances the panels will be rather large and bulky. For example, a common size panel is 10' 10feet .times. 6' .times. 7" which weighs around 330 lbs. These panels are usually packed and shipped in units of three having a shipping weight of over 1,000 pounds. It is desirable that the panels not be unpacked until they are ready to be installed. Thus, the handling equipment within the vessel must be capable of moving a package larger than 10' .times. 6' .times. 21" and weighing in excess of 1,000 pounds. The scaffolding must be constructed to accommodate the handling euqipment and the insulating panels. Each insulating panel is specifically designated for a selected position in the vessel wall.
The inside of the insulation must be covered with a corrosion resistant material which will withstand liquefied natural gas. This corrosion resistant material must also prevent the liquefied natural gas from being contaminated. The material utilized is usually stainless steel or other corrosion resistant material which is formed in panels which are placed on the outside of the insulating layers. The panels are welded together to form a continuous inner stainless steel lining for the vessel. The stainless steel is erosion resistant and prevents the liquefied natural gas from being contaminated. After insulation, the entire inner lining must be completely inspected to determine any leaks or defects. It is desirable that the horizontal levels be relatively open to permit easy movement of men and material. Also the level should be structurally strong to permit the use of machinery such as fork lifts or manipulators which are required for moving, installing, and testing the insulation and inner lining. Studs or other fasteners are attached to the inside of the LNG vessel for holding the insulation in place. Equipment which requires a structurally strong support is utilized for moving and installing the large heavy insulating panels.